1. Technical Field
The present disclosure relates to window frames, and more particularly to commercial grade window frames having structural enhancements which optimize the window sight lines.
2. Description of the Related Art
A wide variety of window system constructions are known in the art. More specifically, single hung, double hung and fixed glazed windows, for example, are commonly used in both residential and commercial applications. The term "single hung" refers to a window design in which the outer frame contains a fixed glazed region and a slidable sash frame movable relative thereto. The term "double hung" refers to a window design having two relatively movable sash frames and no fixed glazed region. Furthermore, slidable sashes may move vertically or horizontally.
To attain a commercial rating, windows must meet or exceed various performance requirements as measured in various tests. For example, the windows are subjected to tests which measure operating force, deglazing, air and water infiltration and structural loads. The criteria for such tests are established by the American Architectural Manufacturers Association ("AAMA") in "Voluntary Specifications for Aluminum, Vinyl and Wood Windows and Glass Doors", published Mar. 1, 1997. The entire contents of these specifications are hereby incorporated by reference. Such test criteria have made it difficult to design commercial rated windows that have narrow sight lines. Accordingly, there is a continuing need for window systems which have as narrow a sight line as possible while remaining within the criteria established for a commercial rating.
Another feature of window frame constructions is the ability of windows to tilt inward to facilitate cleaning of the external side of the sash from the inside of the building. To accomplish this feature, a tilt latch mechanism is typically provided on top of the sash frame. For example, U.S. Pat. No. 4,356,667 to Malachowski discloses a tilt latch for a slidable window sash, wherein the latch engages a vertical channel in the side of the frame until it is movably lifted out of the channel; U.S. Pat. No. 4,400,026 to Brown, Jr. discloses a tilt latch comprising a slide member and resilient biasing means to urge the slide member in a locking position; U.S. Pat. No. 5,139,291 to Schultz discloses a flush mount tilt latch for a sash window; and U.S. Pat. No. 5,618,067 to Carlson et al. discloses a tilt latch device which may be molded in a one-piece construction to minimize the number of parts associated therewith.
However, a problem commonly encountered with conventional latch mechanisms is that they may inadvertently become unlatched leaving the window free to tilt inward. Accordingly, a need exists for an improved tilt latch mechanism which will prevent inadvertent opening of a window.